<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<meta http-equiv="X-UA-Compatible" content="IE=edge">
	<meta name="viewport" content="width=device-width, initial-scale=1.0">
	<title>Document</title>
	<style>
		.box{
			background: fixed;/*不写重复样式，尽量简写样式*/
			margin: 0;/*css样式排序：①首字母②样式长短*/
			font: 100;
			border: darkblue;
			padding: 0;
			opacity: .5;
		}
	</style>
</head>
<body>
	<div class="con">

	</div>
</body>
</html>